PREVIOUS INVESTIGATIONS UPON PLANTS 65 



was not caused by the moisture that gathered on the tube, as was 

 shown by Errera and Steyer with reference to the experiments of 

 Elfving. Positive phototropic response to the phosphorescent light 

 of the radium is also claimed for Vicia Faba seedlings if the activity 

 of the preparation is sufficiently strong. 



In November of the same year (1905) appeared Koernicke's*^ 

 paper on the effect of Rontgen and radium rays on plant tissues and 

 cells. In plants developing from seeds exposed to either radium or 

 X rays, the epidermis of the roots was wrinkled over the entire sur- 

 face. Direct exposure of growing roots produced the same result. 

 The undulatory curvatures of the vascular bundles, present in nor- 

 mally contractile roots, was not observed. Multiplication of nuclei 

 was also observed in cells of the periblem and plerome of exposed 

 roots. 



Cell-studies were made of roots of Vicia Faba and of Pisum 

 sativum, after exposure of i, 2, and 3 days to the radium, and also 

 of roots that developed from exposed seeds. No results followed 

 exposure of the roots for one day, but after an irradiation of two days 

 cell-divisions appeared normal, but less numerous* while treatment 

 for three days sufficed to practically inhibit mitosis. Resting nuclei 

 appeared unaffected. Not until after the roots had ceased growing 

 did peculiar forms appear which could be attributed to the influence 

 of the rays on the chromatin. Here spindles occurred in which the 

 daughter chromosomes were separated from each other with diffi- 

 culty, so that their progress toward the poles was delayed. Forma- 

 tion of the cell-wall occurred normally in exposed tissues, and for this 

 and other reasons it is held that the polynucleate cells resulted from 

 amitosis. 



Flower buds of Liliiim mariagon of various ages, from the 

 youngest to the oldest, were exposed to the rays for varying lengths 

 of time, and fixed at different periods following the exposure. 

 Mitosis was retarded and inhibited, and the reproductive cells were 

 more sensitive than the vegetative cells to the influence of the rays. 

 Numerous irregularities in mitosis were observed. For example, 

 anthers fixed 20 hrs. after irradiation for 5 hrs., showed the nuclear 

 thread of the pollen-mother-cell separated into smaller and more 

 numerous double segments than is normal in the species. The small 

 segments were later drawn together on a normally formed spindle, 

 and, in one instance, on a multipolar spindle. In the subsequent 



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